Radio frequency identification (RFID) technology is used in many different applications, ranging from warehouse logistics (Cheung et al., 2008; herein incorporated by reference in its entirety) to livestock management (Kin Seong Leong et al., 2007; herein incorporated by reference in its entirety). This has been possible due to the flexibility of the technology adapted to different requirements including active and passive tags, near/far field communications or the use of different frequency bands. In essence, all these tags, even though they may lack an internal power source (so-called “passive” tags), nonetheless rely on a silicon chip connected to an antenna. The tags store an identification code that can be retrieved wirelessly by an RFID reader. This setup, although flexible and powerful, has some disadvantages. Among these disadvantages, probably the most important, that limits its widespread application, is the cost. In certain applications, RFID needs to offer a competitive cost that can compete with other identification technologies, such as optical barcodes.
Furthermore, there are important applications for remotely sensing strain, angle, displacement and other related quantities, such as in airframes, bridges and other structures, and even in human performance (e.g. sports medicine and rehabilitation), wherein the movement, angle or displacement of a body part (e.g. an ankle, knee, elbow, shoulder, wrist) should be tracked over time.